----- Original Message -----
From: "Bram Moolenaar" <[EMAIL PROTECTED]>
To: "Stahlman Family" <[EMAIL PROTECTED]>
Cc: <vim@vim.org>
Sent: Wednesday, November 08, 2006 2:00 PM
Subject: Re: Spurious "undefined variable" error generated for certain valid
ternary expressions
Brett Stahlman wrote:
The following expression
var>10?var:10
generates the following errors:
E121: Undefined variable: var:10
E15: Invalid expression: var>10?var:10
The reason is that find_name_end uses eval_isnamec unconditionally to
decide whether a character is a valid variable name character,
with the result that `:' is always gobbled up as part of the variable
name, even if it's not the second character in the name string
(ie, even if it doesn't separate the scope prefix from the variable
name). find_var_ht, on the other hand, will not permit a colon
anywhere but at character index 1 in the variable name; hence, E121,
and ultimately, E15.
Since `:' is part of a valid VimL operator, and is not valid anywhere
other than at index 1 in a non-curly-brace variable name,
there is no ambiguity in the expression shown above. For expressions such as
b>10?b:a
the ambiguity would be resolved according to the relative precedence
of the ternary operator and the variable scope separator (`:'). I
would assume that the precedence of the scope operator would be higher
(since Vim treats it as part of 'variable', whose
precedence is much higher than that of the ternary operator); hence,
in the preceding example, the expression would be evaluated as
(b>10) ? (b:a)
which would indeed be a syntax error...
Should eval_isnamec (or perhaps its caller) take into consideration
the character index when deciding whether `:' is to be
considered part of the variable name?
The docs clearly state:
You should always put a space before the ':', otherwise it can
be mistaken for use in a variable such as "a:1".
Hmm. Ok. I didn't find that text with helpgrep, but I've got Vim7 beta version still on this computer. Perhaps it was added since
then...
Thanks,
Brett S.
In some cases var:10 can be recognized as not being a variable name, but
this leads to undetected mistakes and makes it difficult to add more
scopes later.
It's a good habit to put spaces around ? and : anyway. Unless you never
read back what you've written perhaps.
--
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/// Bram Moolenaar -- [EMAIL PROTECTED] -- http://www.Moolenaar.net \\\
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